Get rid of redundant member function PositionAlgorithm<Strategy>::{upstream,downstream}

Source/core/editing/InputMethodController.cpp

Index: Source/core/editing/InputMethodController.cpp
diff --git a/Source/core/editing/InputMethodController.cpp b/Source/core/editing/InputMethodController.cpp
index 2bf2ad38ce65beff5978579b85649c7055b6896b..b3c08425030c465d61c1ed7b1ed4873dbddfc0bb 100644
--- a/Source/core/editing/InputMethodController.cpp
+++ b/Source/core/editing/InputMethodController.cpp
@@ -270,7 +270,7 @@ void InputMethodController::setComposition(const String& text, const Vector<Comp
     TypingCommand::insertText(*frame().document(), text, TypingCommand::SelectInsertedText | TypingCommand::PreventSpellChecking, TypingCommand::TextCompositionUpdate);
 
     // Find out what node has the composition now.
-    Position base = frame().selection().base().downstream();
+    Position base = mostForwardCaretPosition(frame().selection().base());
     Node* baseNode = base.anchorNode();
     if (!baseNode || !baseNode->isTextNode())
         return;
@@ -305,7 +305,7 @@ void InputMethodController::setComposition(const String& text, const Vector<Comp
 void InputMethodController::setCompositionFromExistingText(const Vector<CompositionUnderline>& underlines, unsigned compositionStart, unsigned compositionEnd)
 {
     Element* editable = frame().selection().rootEditableElement();
-    Position base = frame().selection().base().downstream();
+    Position base = mostForwardCaretPosition(frame().selection().base());
     Node* baseNode = base.anchorNode();
     if (baseNode && editable->firstChild() == baseNode && editable->lastChild() == baseNode && baseNode->isTextNode()) {
         m_compositionNode = nullptr;